The objective of this project is to elucidate mechanisms that control lens cell differentiation during lens morphogenesis and lens growth. Lens development involves the co-ordinated expression of crystallin genes. Experiments have shown that the neural retina, which forms from the inner layer of the optic vesicle, induces the lens epithelial cells to synthesise beta- and gamma crystallins and elongate. The nature of the retinal factor is not known. Nor is it known if the same retinal factor indues lens morphogenesis and alpha-crystallin synthesis. Work is in progress to characterize the retinal factor(s). In addition the sequence of events in the differentiation of epithelial cells into fibre cells in response to the neural retina is being analyzed in explant cultures. Lens morphogenesis begins shortly after the optic vesicle becomes closely associated with the presumptive lens ectoderm. In the electron microscope cellular processes are present in the interspace between the two tissues. Coated pits and vesicles are abundant in the basal cytoplasm of the cells and cell processes. A quantitative study is being carried out to determine if there is a relationship between receptor mediated endocytosis (as indicated by the presence of coated pits and vesicles) and lens morphogenesis and crystallin synthesis.